Neutron Standard Cross Sections for 1H and 6Li from R-Matrix Analyses and Microscopic Calculations for the N-N and 7Li Systems

We present work on the N - N and 7Li systems that is relevant to the international effort to re-evaluate the neutron standard cross sections. The R-matrix analysis of the N - N system also determined the n-p capture cross section for use in BBN modeling of light-element abundances in the early universe with an uncertainty of less than 2.5 %. The R-matrix results for the 6Li(n,t)4He cross section agree qualitatively with a microscopic RRGM calculation that uses semi-realistic N-N potentials. However, they disagree with some cross-section measurements for the reaction, and with another evaluation.